PEP 241: Metadata for Python Software Packages

Andrew Kuchling
Mon, 19 Mar 2001 17:30:19 -0500

PEP: 241
Title: Metadata for Python Software Packages
Version: $Revision: 1.6 $
Author: A.M. Kuchling <>
Type: Standards Track
Created: 12-Mar-2001
Status: Draft
Post-History: 19-Mar-2001


   This PEP describes a mechanism for adding metadata to Python
   packages.  It includes specifics of the field names, and their
   semantics and usage.

Including Metadata in Packages

    The Distutils 'sdist' command will be modified to extract the
    metadata fields from the arguments and write them to a file in the
    generated zipfile or tarball.  This file will be named PKG-INFO
    and will be placed in the top directory of the source
    distribution (where the README, INSTALL, and other files usually

    Developers may not provide their own PKG-INFO file.  The "sdist"
    command will, if it detects an existing PKG-INFO file, terminate
    with an appropriate error message.  This should prevent confusion
    caused by the PKG-INFO and files being out of sync.

    The PKG-INFO file format is a single set of RFC-822 headers
    parseable by the module.  The field names listed in the
    following section are used as the header names.  There's no 
    extension mechanism in this simple format; the Catalog and Distutils
    SIGs will aim at getting a more flexible format ready for Python 2.2.


    This section specifies the names and semantics of each of the
    supported metadata fields.
    Fields marked with "(Multiple use)" may be specified multiple
    times in a single PKG-INFO file.  Other fields may only occur
    once in a PKG-INFO file.  Fields marked with "(optional)" are
    not required to appear in a valid PKG-INFO file, all other
    fields must be present.


      Version of the file format; currently "1.0" is the only
      legal value here.  

      Example: 'Metadata-Version: 1.0'


      The name of the package.  

      Example: 'Name: BeagleVote'

      A string containing the package's version number.  This
      field should be parseable by one of the Version classes
      (StrictVersion or LooseVersion) in the distutils.version

      Example: 'Version: 1.0a2'
    Platform (multiple use)

      A comma-separated list of platform specifications, summarizing
      the operating systems supported by the package.  The major
      supported platforms are listed below, but this list is
      necessarily incomplete.

            POSIX, MacOS, Windows, BeOS, PalmOS.

      Binary distributions will use the Supported-Platform field in
      their metadata to specify the OS and CPU for which the binary
      package was compiled.  The semantics of the Supported-Platform
      are not specified in this PEP.

      Example: 'Platform: POSIX, Windows'

      A one-line summary of what the package does.

      Example: "Summary: A module for collecting votes from beagles."
    Description (optional)

      A longer description of the package that can run to several
      paragraphs.  (Software that deals with metadata should not
      assume any maximum size for this field, though one hopes that
      people won't include their instruction manual as the

      Example: "Description: This module collects votes from beagles\n
                             in order to determine their electoral wishes.\n
                             Do NOT try to use this module with basset hounds; 
                             it makes them grumpy."
    Keywords (optional)

      A list of additional keywords to be used to assist searching
      for the package in a larger catalog.

      Example: 'Keywords: dog puppy voting election'
    Home-page (optional)

      A string containing the URL for the package's home page.

      Example: 'Home-page:'
    Author (optional)

      A string containing at a minimum the author's name.  Contact
      information can also be added, separating each line with

      Example: 'Author: C. Schultz
                        Universal Features Syndicate
                        Los Angeles, CA'

      A string containing the author's e-mail address.  It can contain
      a name and e-mail address in the legal forms for a RFC-822
      'From:' header.  It's not optional because cataloging systems
      can use the e-mail portion of this field as a unique key
      representing the author.  A catalog might provide authors the
      ability to store their GPG key, personal home page, and other
      additional metadata *about the author*, and optionally the
      ability to associate several e-mail addresses with the same
      person.  Author-related metadata fields are not covered by this

      Example: 'Author-email: "C. Schultz" <>'
      A string selected from a short list of choices, specifying the
      license covering the package.  Some licenses result in the
      software being freely redistributable, so packagers and
      resellers can automatically know that they're free to
      redistribute the software.  Other licenses will require
      a careful reading by a human to determine the software can be
      repackaged and resold.

      The choices are:

        Artistic, BSD, DFSG, GNU PL, Lesser GNU PL, "MIT/X11", 
        Mozilla PL, "public domain", Python, Qt PL, Zope PL, unknown,
        nocommercial, nosell, nosource, shareware, other

      The definitions are:
       Python         Python 1.6 or higher license.  Version 1.5.2 and 
                      earlier are under the MIT/X11 license.
       public domain  Software is public domain, not copyrighted.
       unknown        Status is not known 
       nocommercial   Free private use but commercial use not permitted 
       nosell         Free use but distribution for profit by arrangement 
       nosource       Freely distributable but no source code 
       shareware      Payment is requested if software is used
       other          General category for other non-DFSG licenses 

      Some of these licenses can be interpreted to mean the software is 
      freely redistributable.  The list of redistributable licenses is:

      Artistic, BSD, DFSG, GNU PL, Lesser GNU PL, "MIT/X11", 
      Mozilla PL, "public domain", Python, Qt PL, Zope PL, 
      nosource, shareware

      Note that being redistributable does not mean a package
      qualifies as free software, 'nosource' and 'shareware' being

      Example: 'License: MIT/X11'


    This document has been placed in the public domain.